Soil Aggregation and Associated Organic Carbon Fractions as Affected by Tillage in a Rice–Wheat Rotation in North India

Abstract

Soil samples were obtained from a long‐term trial conducted on a silty loam at Sardar Vallabhbhai Patel University of Agriculture & Technology, Modipuram (Meerut), in 2007–2008 to study the effects of various combinations of conventional and zero‐tillage (ZT) and raised‐bed systems on soil aggregation and associated organic C fractions in the 0‐ to 5‐cm and 5‐ to 10‐cm depth in a rice–wheat ( Orysa sativa L.– Triticum aestivum L.) rotation. Macroaggregates increased under a ZT rice (direct‐seeded or transplanted) and wheat rotation with the 2‐ to 4‐mm fraction greater than that of the 0.25‐ to 2‐mm fraction. Bulk and aggregate associated C increased in ZT systems with greater accumulation in macroaggregates. The fine (0.053–0.25 mm) intra‐aggregate particulate organic C (iPOM‐C), in 0.25‐ to 2‐mm aggregates, was also higher in ZT than conventional tillage. A higher amount of macroaggregates along with greater accumulation of particulate organic C indicates the potential of ZT for improving soil C over the long‐term in rice‐wheat rotation.